Chemistry

A simple, green, and efficient approach was used to synthesize 3,4-dihydropyrimidines derivatives. We showed that the application of the planetary ball milling method with a ball-to-reagent weight ratio of 8 for the Biginelli reaction provides 3,4-dihydropyrimidines derivatives with excellent yields (>98%) in a short reaction time from the one-pot, three-component condensation of aldehydes, ethyl acetoacetate, and urea (or thiourea).

Nous décrivons dans le présent travail l'action de 3-hydrazino-2-(N,N-dialkylaminométhyl)propanenitriles sur une série d'iminoesters N-fonctionnalisés. Les produits obtenus sont des triazoles et des triazolones. Les triazoles, présentant deux sites réactifs en positions-1,6, s'intracyclisent en triazolopyrimidines.

The purpose of the present study was to evaluate the performance of milled goethite as an effective nanomaterial for the removal of Cd(II) ions from aqueous solutions. Goethite nanocrystallines powders were prepared by high-energy ball milling with a balls-to-powder mass ratio of 10:1 and for 40 h of milling. X-ray diffraction, Rietveld analysis, and vibrating sample magnetometer are used to characterize the obtained nanopowders followed by tests for toxic metals removal from aqueous solutions. In addition, batch of experiments were performed to determine the adsorption equilibrium, kinetics, and thermodynamic parameters of toxic heavy metal ions by milled goethite. Adsorption data were modeled using Langmuir model, Freundlich equation, pseudo-first-order and pseudo-second-order equations. The adsorption process was found to be highly pH dependent. The adsorption of heavy metal ions reached a maximum value rapidly within 6 min and the adsorption parameters were in good agreement with both the Langmuir and Freundlich isotherms. A maximum Cd(II) ion adsorption capacity was estimated to be 167 mg g −1 at 328 K and a pH of 7. The kinetics of the adsorption process was found to follow the pseudo-second-order rate law. The evaluation of the thermodynamic parameters of milled goethite revealed a spontaneous endothermic adsorption process. Besides, the positive values of the entropy suggest an increase of randomness at the solid-solution interface during the heavy metal ions adsorption.

The present publication investigates the performance of nanocrystalline Ni (15 wt.%)-doped α-Fe2O3 as an effective nanomaterial for the removal of Cd(II) ions from aqueous solutions. The nanocrystalline Ni-doped α-Fe2O3 powders were prepared by mechanical alloying, and characterized by X-ray diffraction and a vibrating sample magnetometer. Batch-mode experiments were realized to determine the adsorption equilibrium, kinetics, and thermodynamic parameters of toxic heavy metal ions by Ni (15 wt.%)-doped α-Fe2O3. The adsorption isotherms data were found to be in good agreement with the Langmuir model. The adsorption capacity of Cd(II) ion reached a maximum value of about 90.91 mg g−1 at 328 K and pH 7. The adsorption process kinetics was found to comply with pseudo-second-order rate law. Thermodynamic parameters related to the adsorption reaction, free energy change, enthalpy change and entropy change, were evaluated. The found values of free energy and enthalpy revealed a spontaneous ...

In this paper, a simple, green, and efficient approach was used to the synthesis of various 2aminothiophenes derivatives with excellent yields (97%) in a short reaction time under ball milling technique without any solvent and any catalyst through Gewald reaction. A direct condensation of an equimolar amount of an ethyl acetoacetat/2-butanone, malononitrile/ethyl cynoacetate, and elemental sulfur under ball milling offered 2-aminothiophenes derivatives in 30 min at 750 rpm.

The objective of this study is to assess the uptake of hexavalent chromium (Cr(VI)) from aqueous solutions onto activated carbons (AC) produced from wood. Two activated carbons are tested, a KOH-activated carbon and a commercial H 3 PO 4 -activated carbon (Acticarbone CXV). The adsorption of Cr(VI) is maximal at the lowest values of pH (pH 3) and increases with temperature for both adsorbents. The KOH-activated carbon shows higher capacity for adsorption of Cr(VI) than Acticarbone. The sorption isotherms fit the Langmuir model accurately. The adsorption reaction was found to obey a pseudo second-order rate. The activation energy and the pre-exponential factor as well as the thermodynamic functions related to adsorption reaction, S • , H • , G • , were determined. Nevertheless, the global reaction rate is probably controlled by the intra-particular diffusion of Cr(VI) and the mass diffusivity of Cr(VI) was evaluated.

The kinetics of pyrolysis of a micro-crystalline cellulose in nitrogen were studied from TGA and DTG data, obtained with two different modes of heating: a dynamic mode at constant heating rates between 1 and 11 • C/min and an isothermal mode at various temperatures, kept constant between 280 and 320 • C. In isothermal mode, it appeared very clearly that the mass depletion shows a sigmoid profile characteristic of an auto-accelerated reaction process. This behaviour is consistent with kinetics of nuclei-growth, well represented by the models of Avrami-Erofeev (A-E) and of Prout-Tompkins (P-T) type. All the other kinetic models commonly applied to the thermal decomposition of solids revealed unsatisfactory. The TGA and DTG data were, thus, found ideally simulated from a reaction scheme consisting in two parallel reactions, termed 1 and 2, each one described by the kinetic law: dx/dt = −A −E/RT x n (1 − 0.99x) m . Reaction 1 is related to the bulk decomposition of cellulose and is characterised by the set of parameters: E 1 = 202 kJ/mol; n 1 = 1; m 1 = 0.48. Reaction 2 is related to the slower residual decomposition, which takes place over approximately 350 • C and affects only 16% by weight of the raw cellulose. With m 2 constrained to 1, the optimised parameters of this reaction were: E 2 = 255 kJ/mol; n 2 = 22. Finally, the proposed model allowed to correctly fit not less than to 10 sets of ATG-DTG data, isothermal and dynamic.

Experiments were performed to evaluate a recent extraction process called the instantaneous controlled pressure drop process (briefly: DIC process: "Détente Instantanée Contrôlée") for extracting some volatile compounds from red cedar wood. This process involves subjecting red cedar chips for a short time (30 s to 5 min) under a steam pressure (1 to 6 bars or from 100 to 165 °C). This first step is followed by a flash decompression toward vacuum (up to 50 mbar). This transition induces a fast evaporation of water and volatile compounds and a cooling effect. The effects of two processing parameters (steam pressure and heating time) on the total extraction yield and on yield of four volatile compounds were evaluated by response surface methodology. The results indicated that the processing pressure is the predominant parameter for global extraction yield of oil (E.O= Extracted Oil) and for yield of the four compounds investigated in this study. The processing time is also a significant parameter but less than processing pressure. Moreover, activated carbon produced from DIC-treated residue revealed larger pore sizes compared to untreated samples.

This work is on the removal of cobalt ions from aqueous solutions by bentonite; a natural ore. It was conducted in batch condition and the results were compared with that of PAC (powdered activated carbon). Its objective was to investigate the possibility of using bentonite economically cheap material- as an alternative to high cost commercial adsorbent material PAC for the removal of cobalt from aqueous solution. The potential of bentonite was assessed for cobalt adsorption from aqueous solutions. Different adsorption isotherms (Langmuir, Freundlich, and Brauner-Emmett-Teller) were applied. The adsorption rate constant (Kad), rate constant for intraparticle diffusion (Kp), pore diffusion coefficient (D), overall reaction rate(K), equilibrium constant (Kc), activation energy (E) and the thermodynamic functions G, H and S were estimated. Also the effect of time, sorbent dose, initial concentration and the pH at different temperatures were studied. The results were interesting, indicating that bentonite is capable of removing cobalt(II) from an aqueous solution. The kinetics of adsorption was investigated as first order diffusion controlled and spontaneous process. The equilibrium time was attains after 70 min for bentonite and the most suitable pH for cobalt removal was found to be 6.

In this work, the removal of cobalt ions from aqueous solutions by carbon soot which is a very cheap industrial
by-product has been studied. Its objective was to investigate the possibility of using carbon soot instead of high cost commercial
adsorbent materials for the removal of cobalt from aqueous solution. Different adsorption isotherms (Langmuir, Freundlich, and
Brauner-Emmett-Teller) were applied. The adsorption rate constant (Kad), rate constant for intraparticle diffusion (Kp), pore
diffusion coefficient (D), overall reaction rate (K), equilibrium constant (Kc), activation energy (E) and the thermodynamic
functions
G◦,
H◦ and
S◦ were estimated. Also the effect of time, sorbent dose, initial concentration and the pH at different
temperatures were studied. The results were interesting, indicating that carbon soot is capable of removing cobalt(II) from an
aqueous solution. The equilibrium time for cobalt(II) adsorption on soot is larger than that on powdered activated carbon. Cobalt
adsorption is pH dependent. The kinetics of adsorption was investigated as first order diffusion controlled and spontaneous
process

The removal of Nickel (Ni2+) and Zinc (Zn2+) from their aqueous solution
mixtures by adsorption onto carbon soot was investigated and compared with their
adsorption on powdered activated carbon. Experiments were carried out at a
constant initial concentration of each heavy metal ion, constant pH and constant
adsorbent dose. Results from kinetic models (Lagergren equation and Weber Morris
plot) showed that increasing of Ni2+ and Zn2+adsorption with increasing
temperature. Activation energy measurements (Arrhenius equation) revealed a
physical adsorption. The enthalpy of adsorption process was measured through
Van’t Hoff equation revealing that endothermic adsorption process. The adsorption
of Ni2+ was higher than that for Zn2+ which can be explained through higher value of
ΔH in case of Zinc. Results suggested that carbon soot is a promising adsorbent for
adsorption of metal ions from aqueous solution mixture at high temperature.

Friendly environmental processes have to be adopted to produce value added
materials from by-product wastes. The present work is aimed to reclaim animal fat from
hides fleshing wastes (rich in fats) that produced as a side-product in leather tanneries.
The fat was separated from fleshing wastes under optimal conditions (fleshing : water 1:
1.75 w/v, 90°C and 3 hrs stirring time).Local bentonite clay was instigated in order to
improve bleaching capacity of reclaimed fat. The clay was evaluated rather than
characterized using ICP Spectrometer. The absorbance efficiency and bleaching capacity
of the clay were improved via sulphuric acid activation. The color and smell of the
bleached fat were strongly enhanced. Chemical evaluation of the reclaimed purified fat
indicates that it has a great industrial application potential such as cosmetics, soap and
surfactants manufacture. Thus, this work try to find away to save resources, reduce
pollution and cost disposal.

Modern Industries’ effluents cause water contamination with heavy metals. In this
work, bentonite was used for nickel(II) removal from aqueous solution compared with
commercial activated carbon. The adsorption isotherms (Langmuir, Freundlich, and
Brauner-Emmett-Teller) were applied. The rate constant of adsorption, the rate constant
for intraparticle diffusion, pore diffusion coefficient, overall reaction rate, equilibrium
constant and the thermodynamic parameters ΔGᵒ, ΔHᵒ and ΔSᵒ were evaluated. Also the
effect of time, Sorbent dose, initial concentration and the pH at different temperatures
were studied. The results were promising, indicating that bentonite is capable of
removing nickel(II) from aqueous solution. The equilibrium time for nickel(II) adsorption
by bentonite is larger than that by the powdered activated carbon and highly pH
dependent. The kinetics of adsorption were investigated as first order diffusion controlled
and spontaneous process.

2-Hydroxy Schiff base ligands and their complexes derived from the reaction of derivatives of salicylaldehyde with amines have been extensively studied in great details for their various crystallographic, structural and magnetic features. (Yildiz, Kilic et al. 1998, Sunatsuki, Motoda et al. 2002) Schiff bases constitute an important class of ligands, which have very rich and extensive chemistry, reviewed recently by Vigato and Tamburini. (Vigato and Tamburini 2004) Metal complexes of Schiff bases have found diverse applications in addition to interesting structural chemistry. Chelation causes drastic change in the biological properties of the ligands and also the metal moiety. It has been reported that chelation is the cause and cure of many diseases including cancer. A number of Schiff base complexes (Arion, Reisner et al. 2003, Drabent, Bialoska et al. 2004)have been tested for antibacterial activities and they have been found antibacterial (Kabeer, Baseer et al. 2001, More, Bhalvankar et al. 2001), antifungal (Singh and Dash 1988, More, Bhalvankar et al. 2001), anticancer (Desai, Desai et al. 2001) and herbicidal(Samadhiya and Halve 2001) activities.We report in this article the in situ synthesis and characterization of the Cu(II), Cd(II), Fe(III), Ni(II), Co(II), Zn(II) and Mn(II) of the 2-((2-(2,4-dinitrophenyl)hydrazono)methyl)phenol. The coordination behavior of the Schiff base ligand towards metal ions was investigated via IR, UV, ESR as well as conductivity and magnetic moments measurements. The antibacterial and antifungal activities of the compounds showed that, metal complexes exhibited a greater inhibitory effect than the ligand

Natural bentonite clay from Saudi Arabia was used to remove cobalt from aqueous solution. The clay samples were first characterized for their chemical composition and structure. Batch sorption studies were then conducted to assess their capacity to remove cobalt. The effect of contact time, initial analyte concentration, bentonite dose and temperature on the adsorption was investigated. The results showed that equilibrium was attained in 60 minutes. The metal adsorption was fitted to a Langmuir isotherm model and the maximum monolayer adsorption capacity was found to be 19.85 mg g−1 at 333 K. The pseudo-second-order kinetic model provided the best correlation to the experimental data. The application of an intra-particle diffusion model revealed that the adsorption mechanism of the cobalt ions is a rather complex process and that diffusion is involved in the overall rate of the adsorption process, but it is not the only rate-controlling step. The activation energy, Ea, ranged betwee...

In this work, the effect of electrolyte pH on the composition and microstructure of Zn-Ni-Mn films were investigated using EDS, XRD and SEM. The composition of Zn-Ni-Mn films are greatly affected by the electrolyte pH. Low electrolyte pH (≤1) favors the normal deposition with very low amounts, while higher electrolyte pH leads to the anomalous deposition which decreases with increasing pH. The films prepared at low pH values show a very poor quality with rough surface while those electrodeposited at high pH value (2.5~5) are generally quite smooth, uniform and compact. Galvanostatic measurements for electrodeposition, cyclic voltammetry (CV) were used to the anodic and cathodic behavior of alloy to study the potential ranges. Anodic linear sweep voltammetry (ALSV) technique was used for the phase structure determination. The effect of pH on the film quality and corrosion performances in the films, the corrosion test was performed by the potentiodynamic anodic polarization method. Th...